My neck hurts

i recently started a jump program that is supposed to improve my vertical for basketball. There is one particular excercise that i do that makes my neck hurt, right where my head and neck meet and its only on the left side. Ill start doing the excercise and within 5-1o jumps it feels like someone has kicked me in the back of the head,it continues to throb for hours and sometimes still hurts the next day, whats up with that